KVM: s390: add proper locking for CMMA migration bitmap

[sfrench/cifs-2.6.git] / arch / s390 / kvm / kvm-s390.c

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 98ad8b9e036093c8a784cfc0dfd3887e925c6357..52880e980a336a80263cd83c70aeabaad6726ea1 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1,11 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
- * hosting zSeries kernel virtual machines
+ * hosting IBM Z kernel virtual machines (s390x)
  *
- * Copyright IBM Corp. 2008, 2009
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License (version 2 only)
- * as published by the Free Software Foundation.
+ * Copyright IBM Corp. 2008, 2017
  *
  *    Author(s): Carsten Otte <cotte@de.ibm.com>
  *               Christian Borntraeger <borntraeger@de.ibm.com>
@@ -769,7 +766,7 @@ static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
 
 /*
  * Must be called with kvm->srcu held to avoid races on memslots, and with
- * kvm->lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
+ * kvm->slots_lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
  */
 static int kvm_s390_vm_start_migration(struct kvm *kvm)
 {
@@ -795,11 +792,12 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
 
        if (kvm->arch.use_cmma) {
                /*
-                * Get the last slot. They should be sorted by base_gfn, so the
-                * last slot is also the one at the end of the address space.
-                * We have verified above that at least one slot is present.
+                * Get the first slot. They are reverse sorted by base_gfn, so
+                * the first slot is also the one at the end of the address
+                * space. We have verified above that at least one slot is
+                * present.
                 */
-               ms = slots->memslots + slots->used_slots - 1;
+               ms = slots->memslots;
                /* round up so we only use full longs */
                ram_pages = roundup(ms->base_gfn + ms->npages, BITS_PER_LONG);
                /* allocate enough bytes to store all the bits */
@@ -824,7 +822,7 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
 }
 
 /*
- * Must be called with kvm->lock to avoid races with ourselves and
+ * Must be called with kvm->slots_lock to avoid races with ourselves and
  * kvm_s390_vm_start_migration.
  */
 static int kvm_s390_vm_stop_migration(struct kvm *kvm)
@@ -839,6 +837,8 @@ static int kvm_s390_vm_stop_migration(struct kvm *kvm)
 
        if (kvm->arch.use_cmma) {
                kvm_s390_sync_request_broadcast(kvm, KVM_REQ_STOP_MIGRATION);
+               /* We have to wait for the essa emulation to finish */
+               synchronize_srcu(&kvm->srcu);
                vfree(mgs->pgste_bitmap);
        }
        kfree(mgs);
@@ -848,14 +848,12 @@ static int kvm_s390_vm_stop_migration(struct kvm *kvm)
 static int kvm_s390_vm_set_migration(struct kvm *kvm,
                                     struct kvm_device_attr *attr)
 {
-       int idx, res = -ENXIO;
+       int res = -ENXIO;
 
-       mutex_lock(&kvm->lock);
+       mutex_lock(&kvm->slots_lock);
        switch (attr->attr) {
        case KVM_S390_VM_MIGRATION_START:
-               idx = srcu_read_lock(&kvm->srcu);
                res = kvm_s390_vm_start_migration(kvm);
-               srcu_read_unlock(&kvm->srcu, idx);
                break;
        case KVM_S390_VM_MIGRATION_STOP:
                res = kvm_s390_vm_stop_migration(kvm);
@@ -863,7 +861,7 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm,
        default:
                break;
        }
-       mutex_unlock(&kvm->lock);
+       mutex_unlock(&kvm->slots_lock);
 
        return res;
 }
@@ -1753,7 +1751,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
                r = -EFAULT;
                if (copy_from_user(&args, argp, sizeof(args)))
                        break;
+               mutex_lock(&kvm->slots_lock);
                r = kvm_s390_get_cmma_bits(kvm, &args);
+               mutex_unlock(&kvm->slots_lock);
                if (!r) {
                        r = copy_to_user(argp, &args, sizeof(args));
                        if (r)
@@ -1767,7 +1767,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
                r = -EFAULT;
                if (copy_from_user(&args, argp, sizeof(args)))
                        break;
+               mutex_lock(&kvm->slots_lock);
                r = kvm_s390_set_cmma_bits(kvm, &args);
+               mutex_unlock(&kvm->slots_lock);
                break;
        }
        default:
@@ -3811,6 +3813,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                        r = -EINVAL;
                        break;
                }
+               /* do not use irq_state.flags, it will break old QEMUs */
                r = kvm_s390_set_irq_state(vcpu,
                                           (void __user *) irq_state.buf,
                                           irq_state.len);
@@ -3826,6 +3829,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                        r = -EINVAL;
                        break;
                }
+               /* do not use irq_state.flags, it will break old QEMUs */
                r = kvm_s390_get_irq_state(vcpu,
                                           (__u8 __user *)  irq_state.buf,
                                           irq_state.len);